During the normal operation of railroad cars, the conventional draft gear coupling adjacent cars together can accept the compression or buff loads tending to move these cars together. These loads can be on the order of 65,000 to 75,000 pounds. However, under emergency stopping operation or in the event of collision, the conventional couplings cannot accept the greatly increased buff forces and therefore cannot absorb the kinetic energy tending to move the cars together. Thus, the cars can override the coupling resulting in collision therebetween and potential injury to passengers.
While there have been prior art energy absorbing devices used in conjunction with conventional draft gear couplings or by themselves, none of these are completely satisfactory. Thus, some of these prior art devices do not uniformly absorb high energy loads and therefore are unreliable and unpredictable. In addition, many of these prior art devices are not easily adjustable for various conditions and therefore can fail when encountering extremely high buff forces. Moreover, many of these prior art devices are subject to jamming.
Examples of these prior art devices for absorbing energy between relative movement of two bodies are disclosed in the following U.S. Pat. Nos. 1,765,200, issued to Bullough on June 17, 1930; 2,277,881, issued to Olander on Mar. 31, 1942; 2,615,373, issued to Pegard on Oct. 28, 1952; 2,802,580, issued to Larsson on Aug. 13, 1957; 2,811,385, issued to Butler on Oct. 29, 1957; 2,837,176, issued to Dropkin on June 3, 1958; 3,097,725, issued to Peterson on July 16, 1963; 3,305,452, issued to Remoleur on Feb. 21, 1967; and 3,751,089, issued to Lefeuvre on Aug. 7, 1973.
The Larsson patent discloses a conventional coupler for railroad cars which merely has shearable bolts, which shear when the buff forces reach a predetermined value; however, this device does not provide a uniform energy absorption between the cars. The Pegard patent discloses a safety stopping device for movable machine-tool members comprising an annular member receiving a frustoconical section on another relatively movable member; however, this device does not provide a uniform or predictable absorption of energy. A similar problem is found in the Lefeuvre patent which in FIG. 3 discloses a plurality of hooks on a first member engaged in a plurality of apertures in a second member, whereby energy is absorbed upon relative movement of the two members by a ripping of the member having the apertures therein by means of the hooks engaged therein.